1. Field of the Invention
This invention relates to a circuit for charging a release magnet energizing capacitor in an electromagnetic release camera.
2. Description of the Prior Art
Heretofore, in an electromagnetic release camera, switching transistors serially inserted between a DC power source and a release magnet energizing capacitor have been turned on to charge the release magnet energizing capacitor from the power source and during the shutter release, a release switch has been closed to cause the charge stored in the capacitor to be discharged to the release magnet coil. In cameras, from the requirement in actual armor, there was a tendency to employ integrated circuit (IC) elements and the above-described switching transistors are not exceptional. Transistors used in an IC are lateral transistors (operationally, PNP transistors) for the sake of reduced cost, but the ON resistance (saturation resistance) of such transistors becomes relatively high and therefore, if they are used for switching, there is a disadvantage that they take a longer charging time for the capacitor than discrete transistors. In contrast, if the switching transistor is emitter-grounded and the capacitor is used as the load of the emitter, then the internal resistance becomes smaller due to the negative feedback action, but there is a saturation voltage (collector-emitter voltage) of the order of 0.7 volt and therefore, a voltage drop occurs to give rise to a disadvantage that the capacitor is not sufficiently charged up to the source voltage. Also, in the former case, there is a fear that the charging voltage is deficient when continuous photography at short intervals is to be effected.